Ex7:Skin & Membranes

Ex7: The Skin & Other Body Membranes

I. Introduction/Background Information

        Refer to the Lab worksheet : https://sites.google.com/site/physiolablist/

There are several sections to this lab, generally designed to assist students in understanding the structures & functions of skin & other body membranes. The objectives of this lab are:

1. to recount important functions of the skin/integumentary system
2. to recognize and name the following structures from a slide, model or diagram
• epidermis (including strata), 
• dermis (papillary & reticular layers
• hair follicles & hair
• sebaceous glands & sweat glands
3. to compare the properties of the dermis & epidermis
4. to describe the distribution and function of the sebaceous glands, sweat glands, and hair 
5. to differentiate between eccrine & apocrine sweat glands
6. to ennumerate the factors determining skin color
7. to describe the function of melanin
8. to compare the structure and function of the major membrane types
9. to list the general functions of each membrane type and note its location in the body
10. to recognize by microscopic examination epidermal, mucous, and serous membranes

II. Hypothesis

Part 1: Basic structure of the skin: If students read about structures as they locate them on a skin model then they will be able to write out a response to each objective
Part 2: Appendages of the Skin: If students examine a prepared slide of human skin then they will be able to identify skin structures on a drawing.
Part 3: Plotting the Distribution of sweat glands: If bond paper is taped to skin coated with iodine and left for 20 minutes, then a distribution of sweat glands will be mapped out because the sweat glands will dissolve the iodine, which will then be absorbed by the paper.  As it reacts with the starch in the bond paper each sweat gland will produce a blue/black dot.
Part 4: Classification of Membranes: If students examine slides from trachea and small intestine, heart, as well as a freshly cut joint, then they can compare mucous, serous and synovial membranes.

III. Materials

    “See Lab instructions”

IV. Procedure

“See Lab Instructions” (you may include pictures of procedure)

Part 1: Basic structure of the skin:

Skin slide

Human Skin Slide

Part 2: Appendages of the Skin:
Part 3: Plotting the Distribution of sweat glands:
Part 4: Classification of Membranes:

pseudostratified ciliated columnar epithelium

mucosa of trachea

mucosa of small intestine

drawing of one villus

pericardium (around the heart)

V. Results/Observation/Data
List answers to questions from each section of the lab

Part 1: Basic structure of the skin:

• There are no questions to answer for this part.

Part 2: Appendages of the Skin:

• The stratified squamous in this exercise is different from the stratified squamous in exercise 6 because it is a slide from the skin and it shows a larger section, which has the dermis and epidermis. It also shows hair protruding from the epidermis and glands within the dermis.
• The one in this exercise is keratinized, or hardened, in order to prevent water loss from the body surface.  The one in exercise 6 was not keratinized because the other stratified squamous slide was not from the skin. 

Part 3: Plotting the Distribution of sweat glands:

• The medial aspect of the palms have a greater density of sweat glands than the forearm. 

Labeled  Pictures:

Part 4: Classification of Membranes:
Mucous Membrane

• The mucosa of of the small intestine contains goblet cells and the mucosa of the trachea does      not.
• The role of the mucosa of the trachea is to secrete large amounts of protective, lubricating mucus and the role of the mucosa of the small intestine is to secrete mucus to promote movement and effective diffusion.
• They are similar because they both secrete mucus and they are both made out of epithelium cells that rest on the lamina propria.
• Mucus membranes do have a high regeneration capacity because epithelial cells regenerate faster than other types.

Serous Membranes

• We have seen both simple squamous epithelium and areolar connective tissue.
• The parietal pericardium is around the heart and the visceral pericardium is the cavity in which the heart resides in.  
• The pleura lines the lungs and the peritonea covers the thoracic cavity.  
• The peritoneum lines the abdominal cavity.

VI. Conclusion: Respond to each objective. What did you learn?

1.  What are the important functions of the skin/integumentary system?

• Protect the body’s internal living tissues and organs
• Protect against invasion by infectious organisms
• Protect the body from dehydration
• Protect the body against abrupt changes in temperature, maintain homeostasis
• Help excrete waste materials through perspiration
• Act as a receptor for touch, pressure, pain, heat, and cold
• Protect the body against sunburns
• Generate vitamin D through exposure to ultraviolet light
• Store water, fat, glucose, and vitamin D

1. Can you recognize and name the following structures from a slide, model or diagram?- Yes
• epidermis (including strata), 
• dermis (papillary & reticular layers
• hair follicles & hair
• sebaceous glands & sweat glands
2. Compare the properties of the dermis & epidermis- The epidermis is the outer layer and is made of stratified squamous epithelium that is capable of keratinizing.  The dermis is mostly made of dense connective tissue and is vascular.
3. Describe the distribution and function of the sebaceous glands, sweat glands, and hair- The sebaceous gland secretes oil called sebum, which lubricates our skin and hair.  Sweat glands are used for body temperature regulation and they are distributed all around the body with more in some areas compared to others.  Hair is a flexible epithelial structure which helps for protection and warmth.  All of these accessories of the skin are distributed throughout the body.
4. Differentiate between eccrine & apocrine sweat glands- Eccrine sweat glands produce sweat all over the body, while apocrine sweat glands are mostly present in the axillary and genital areas and they secrete a fatty acid and protein combination, which increases with puberty. 
5. Ennumerate the factors determining skin color- The amount and kind of melanin in the epidermis, the amount of carotene deposited in the stratum corneum and subcutaneous tissue, the amount of oxygen-rich hemoglobin in the dermal blood vessels.  
6. Describe the function of melanin- Melanin is a pigment that ranges in color from yellow to black and it is produced by melanocytes.  When the skin is exposed to sunlight, the melanocytes are stimulated and they produce more melanin which tan your skin.  
7. Compare the structure and function of the major membrane types- Cutaneous membrane is composed of keratinizing stratified squamous epithelium and dense connective tissue.  Mucous membranes are composed of epithelium resting on a loose connective tissue membrane.  Serous membranes are composed of a layer of simple squamous epithelium resting on a layer of areolar connective tissue.
8. List the general functions of each membrane type and note its location in the body- Mucous: absorption and secretion; lines body cavities that open to exterior.  Serous: frictionless movement of organs; lines open body cavities that are closed to the exterior.  Cutaneous: protection; skin. Synovial: smooth surface and secretion; lines fibrous capsules surrounding joints.
9. Can you recognize by microscopic examination epidermal, mucous, and serous membranes? Yes, after looking at the pictures of the slides above, I can recognize by microscope examination epidermal, mucous, and serous membranes.